linux-kernel - Re: [PATCH v2] s390/pkey: prevent overflow in size calculation for memdup

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Message-ID: <af8efb80-a886-4fdb-80a9-e889cfbefe74@linux.ibm.com>
Date: Thu, 12 Jun 2025 11:10:48 +0200
From: Holger Dengler <dengler@...ux.ibm.com>
To: Fedor Pchelkin <pchelkin@...ras.ru>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>
Cc: Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Ingo Franzki <ifranzki@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] s390/pkey: prevent overflow in size calculation for
 memdup_user()

On 11/06/2025 21:20, Fedor Pchelkin wrote:
> Number of apqn target list entries contained in 'nr_apqns' variable is
> determined by userspace via an ioctl call so the result of the product in
> calculation of size passed to memdup_user() may overflow.
> 
> In this case the actual size of the allocated area and the value
> describing it won't be in sync leading to various types of unpredictable
> behaviour later.
> 
> Use a proper memdup_array_user() helper which returns an error if an
> overflow is detected. Note that it is different from when nr_apqns is
> initially zero - that case is considered valid and should be handled in
> subsequent pkey_handler implementations.
> 
> Found by Linux Verification Center (linuxtesting.org).
> 
> Fixes: f2bbc96e7cfa ("s390/pkey: add CCA AES cipher key support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>

Reviewed-by: Holger Dengler <dengler@...ux.ibm.com>

-- 
Mit freundlichen Grüßen / Kind regards
Holger Dengler
--
IBM Systems, Linux on IBM Z Development
dengler@...ux.ibm.com